The present invention relates to liquid sample taking devices of the type provided with an elongated, usually tubular container portion which is provided at its normally lower end with a closing plug mounted at the end of a rod passing through the container and manipulated from the exterior of the container at the other, normally upper, end of the container.
A device of the above kind is typically used to take samples of hazardous chemicals. It is important that the device meet several prerequisites. It should be capable of withdrawing from the body of liquid to be sampled a composite sample, i.e. a sample which corresponds as closely as possible to the arrangement of the sampled body. The device should be capable of minimizing cross-contamination which could adversely affect the sample composition, hence sample results. In other words, it must be capable of quick and easy cleaning of its parts which come into contact with the sampled matter, or inexpensive enough to economically allow the disposal of its parts coming into contact with the sampled liquid. That is to say, at least those parts which are to come into contact with the sampled liquid should be as inexpensive as possible. Another desired feature is the possibility of an easy, quick and reliable assembling and disassembling of the parts contacting the liquid with or from the rest of the device so that the release can be more compatible with the liquid being sampled.
Many attempts have been made to provide a liquid sampling device as mentioned above, which would meet many of the above requirements. For instance, U.S. Pat. No. 1,603,712 issued Oct. 19, 1926 (Peck) discloses a sampling device used in measuring quantities of oil. The quantity determination is corrected for a temperature factor, and the device is designed to take, at any depth of a container, an amount of liquid proportional to the cross-sectional area of the container at that depth. When viewed from the standpoint of the present invention, the device is not only expensive to produce and cumbersome to operate but also fails to provide a smooth passage for the sampled liquid. Another device, U.S. Pat. No. 1,857,537 issued May 10, 1932 (Frank et al.) is disadvantageous as it requires a guiding bracket within the sample retaining container. Any sample flowing into the container from the bottom end must be disturbed by this obstruction. Besides, the mechanism for holding the closing plug sealingly against the container utilizes a camming surface engaged by a pin in the plunger rod. This mechanism may fail to provide good sealing engagement in one extreme, or may subject the plug to unnecessary compression causing premature wear of the closure member in the opposite extreme. U.S. Pat. No. 2,302,884 issued Nov. 24, 1942 (O'Neill) discloses a transparent oil level indicator which is allowed to rest at the bottom of an oil case while oil flows into its lower end. The lower end is closed by exerting pressure on the upper end of the casing. As in the preceding example, the inside of the container section is provided with a plurality of protrusions providing guide for the rod operating the cover at the bottom of the container. U.S. Pat. No. 2,554,832, issued May 29, 1951 (Kulp) presents another complex structure expensive to produce and thus not suitable for discarding, or difficult to maintain clean and thus prone to causing cross-contamination. The device is described as being suitable for determining temperature of stored liquids, and also being used in sampling at a selected elevation. Finally, reference may be had to U.S. Pat. No. 4,594,905, issued Jun. 17, 1986 (Roberts) and showing a somewhat complex liquid analyzer which also allows for sampling at a selected elevation, and includes a temperature indicating unit, among other things. This patent contains reference supporting the statement in the introduction of this description, namely that the field of sampling devices of this type is crowded.
In summary, the prior art of which the above references are believed to be most relevant, does not meet many of the above requirements. The closure activating mechanism parts, such as guide rings and travel stops are likely to interfere with fluid flow into the tubular element. If a non-homogeneous mixture was to be sampled, the flow rate of each component of the mixture into the tube would vary according to its physical properties (density, viscosity, etc.). A composite sample, from a drum for example, could not be obtained from a single draw, when using the prior art devices. This is why the prior art devices are useful only for taking samples at predetermined depths. The likelihood of cross-contamination increases when there are more internal parts that come into contact with the fluid being sampled. Most prior art devices have complicated internal structures.
To be useful as composite samplers for hazardous chemicals, the prior art devices would have to be used to take several samples from one container, at different depths. These samples would then have to be combined to provide a composite sample. The prior art samplers would have to be cleaned after each of these draws. To take several samples of waste from the same container, using a complicated decontamination procedure between samples, would be impractical. The procedure, if used for sampling hazardous chemicals, would likely be too tedious or dangerous to be practical. If the rod guides of, say, U.S. Pat. No. 1,857,537 were moved closer to the activating mechanism, i.e. away from the closure element, lateral stability of the rod would likely be reduced giving rise to difficulties with proper sealing of the closure member.
Components of the closure activating mechanism of the liquid samplers of the prior art are physically connected to the tubular elements of these devices. This construction makes it difficult to adapt the material of which the samplers components are made to the chemicals to be sampled. It is impossible for one sampler alone to be compatible with sufficiently many different chemical classes. Either several samplers made of different materials would have to be kept handy when using prior art configurations, or all incompatible components of the one sampler would have to be changed after each sample is taken.